The experiments proposed in this application build upon and extend research initiated under a previous grant aimed at developing and testing empirically derived neural network models of aging. The major aim is to specify the mechanisms that account for age-related differences in practice-related improvements in learning and skilled performance. Our focus is on the description of age-related inter-individual differences in learning and skill acquisition in terms of the efficiency of a memory-based learning mechanism and the efficiency of computing algorithmic solutions. That is, which mechanism of learning are degraded and which mechanisms of skilled performance are preserved across the adult life-span? During the four years of this project, about 400 women and men between the ages of 20 and 70 years will be tested in four experiments, to examine session-by-session changes in the speed, variability, and accuracy of performance, as well as changes in the shape of the distributions of response times. Analyses of age-related individual differences along these measures across multiple practice sessions are expected to reveal shifts from algorithmic computation to memory based processing.